Flow divider for throttles

ABSTRACT

A device is disclosed for reducing flow distortion in a fuel control throttle valve consisting essentially of a flow guide disposed within a throttle valve. The flow guide reduces the effects of random turbulence and flow distortion associated with high fuel-flow velocities and small radius turns in the flow ducting in miniaturized housing controls. Practical design of the flow guide is critical. Most importantly, the guide must fall within about a 25* to 55* angle of the metering window.

' United States Patent 732,776 7/1903 Neumeyer Melvin L. Perkins Long Meadow, Mass.;

Robert Sherman, West Hartford, Conn. 840,237

July 9, 1969 Aug. 17, 1971 United Aircraft Corporation East Hartford, Conn.

inventors Appl. No. Filed Patented Assignee FLOW DIVIDER FOR THROTTLES 7 Claims, 2 Drawing Figs.

11.8. C1. 137/2, I 137/l17,25l/i20 int. Ci. 605d 11/00 Field of Search 137/2, 14,

References Cited UNlTED STATES PATENTS 1,560,771 11/1925 Feichter l37/625.38

2,034,573 3/1936 G0ehring.... l37/625.38 X

2,957,488 10/1960 Farkas 137/1 17 FORElGN PATENTS 514,051 11/1930 Germany 137/625.39

Primary Examiner- Robert G. Nilson Attorney-Edmund C. Meisinger ABSTRACT: A device is disclosed for reducing flow distortion in a fuel control throttle valve consisting essentially of a flow guide disposed within a throttle valve. The flow guide reduces the effects of random turbulence and flow distortion associated with high fuel-flow velocities and small radius turns in the flow ducting in miniaturized housing controls. Practical design of the flow guide is critical. Most importantly, the guide must fall within about a dowi ' BYPASS FLOW PRESSURE REGULATING VALVE 25 to 55 angle of the metering win- PATENTEgmmmn v I 85953552 F/G. I INTEGRATED v SIGNAL UPSTREAM TOTAL PRESSURE 23 27 STATIC PRESSURE BYPASS FLOW PRESSURE REGULATING VALVE INVENTORS MELVIN L.PER|\INS ROBERT SHERMAN ATTORNEY TOTAL FLOW FROM FUEL PUMP FLOW DIVIDER FOR THROTTLES BACKGROUND OF THE INVENTION This invention relates to fuel controls and more specifically relates to improved throttle valves in fuel controls for gas turbine power plants.

I-Iydromechanical fuel controls used to regulate the thrust output of gas turbine engines are designed to provide reliable and accurate control of the engine within the operational limits'of the engine at minimal size and weight. Fuel controls commonly govern engine starting, acceleration, and deceleration and maintain selected steady-state engine rotor speeds over a range of aircraft altitudes and airspeeds. The control responds to various flight parameters which are fed into the computing system of the control. The computing system positions at throttle valve to control the fuel fed to the engine. This positioning is executed by a variety of techniques wherein an integrated signal is directed to the throttle valve to change the metering area in the throttle valve to provide the desired fuel flow.

As stated, fuel is directed to a throttle valve which is com-'- monly a window-type valve positioned by an integratedsignal from the computing system. Fuel may be metered to the engine by maintaining a constant pressure difference across the throttle valve metering area with a pressure regulating system and by simply varying the window openings to increase or decrease fuel flow. An engine-driven fuel pump directs fuel to either the throttle valve or to the pressure regulating valve as shown, for example, U.S. Pat. No. 2,822,666 to Best at FIG. 4.

The state of the art controls have been limited by the flow velocities which can be tolerated in the fuel passages. Random turbulence and flow distortion in miniaturized housings have prevented designers from reducing the size of the passages resulting'in limitations in the size and weight of the fuel control. The problem of random flow fluctuation and turbulence carries through to the throttle valve metering windows, Flow disturbances cause transient variations in the discharge coefficient at the windows that further contribute to flow perturbations. Fluctuation amplitudes of up to :2 percent of nominal flow have been caused by these effects. In some of the larger engines, a 4 percent fluctuation in flow can amount to fuel flow variations as high as 1,000 lbs. per hour. It is evident that such variations are unacceptable in high performance engines.

I SUMMARY OF THE INVENTION It is an object of this invention to reduce the effects of ran-- dom turbulence and flow distortion in miniaturized housing fuel controls.

Another object of this invention is the reduction of fuel flow fluctuation in the form of a unique flow guide for redistributing flow through the metering windows of a throttle valve in a dependable and repeatable manner.

A further object of this invention is the provision of a flow guide within a throttle valve to partition flow thereby reducing the swirl of incoming flow to the throttle valve and to redirect the flow toward the metering windows thereby facilitating the turning of the flow as it passes through the throttle valve and out'through the metering windows. The most important aspect of.-this invention lies in locating the flow guide so that the angle between the flow guide and the metering windows falls within about the 25 to 55 range. Additionally, the upstream pressure must be taken after the flow is straightened.

In accordance with this invention, a flow guide is disposed within and generally attached to the inner throttle valve element. Theflow guide has a base portion adjacent the metering-window opening which is adapted to turning the flow through the windows and a partition portion extending lengthwise of the inner valve element for straightening the flow. The flow guide is aligned so that the angle between the partitionand the effective window opening area is preferably between 25 and 55. The ratio of the length of. the guide to the internal diameter of the inner element should generally be greater than about 2. The guide length cannot be reduced significantly without incurring unacceptable flow fluctuations. Since fuel is'metered by maintaining a constant pressure difference across the throttle valve'metering area, suitable pressure sensing ports must be located upstream of the throttle valve and downstream of the throttle valve. The upstream sensing port is preferably a total pressure probe inserted directly into the flow within the throttle, valve. Theupstream sensing port cannot be downstream of the metering windows and cannot be upstream of the throttle valvesince the flow fluctuations and pressure losses would lead to unreliable pressure readings.

Other advantages and features of the present invention will become more apparent from the accompanying drawings and from the following detailed description of a preferred embodiment thereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic partly in section of a throttle valve incorporating the flow guide of the present invention.

FIG. 2 is a sectional view taken along the lines 2-2 in FIG. 1 showing the angular location of the flow guide.

DESCRIPTION OF THE PREFERRED EMBODIMENT dows I8. The inner element 16 has a close fitting sleeve 20.

The outer sleeve 20 has similar metering windows 22 so that fuel is directed up through the inner element and passes out wardly through the metering windows into collector 24. Thereafter it is directed through downstream duct 26 to the engine fuel nozzles. This approach is well known and is taught in the Best patent referred to herein.

The throttle valve has a constant pressure differential maintained across it by the pressure regulating system. Fuel is directed to either the main throttle valve or bypasses through the pressure regulating valve which, in effect, regulates the pressure upstream of the metering windows. The movable element 1 6 is controlled by a signal which is shown as the integrated signal input supplied through lever 28. The integrated signalfdepends upon various parameters such as engine burner pressure, engine speed, compressor inlet pressure,compressor inlet temperature, power lever and thelike that work in conjunction with each other to produce a net torque on the multiplying lever 28. A balancing torque is generated by spring 30 that is a function of the throttle valve position. As long as the net torque is zero, the throttle valve'movable element 16 does not change its position. Any net torque change displaces the valve element 16 and causes the element to move until the balancing torque is equalized by the spring force. It is apparent that axial translation of the inner valve element 16 relative to the sleeve 20 changes the effective area of the corresponding window openings 18 and 22 thereby increasing or decreasing the fuel flow. The effect of maintaining a constant pressure head across the throttle valve metering windows results in a direct relationship between fuel flow and the area of the metering valve'windows. Window area in turn is directly related to the axial position of the inner element and sleeve relative to each other.

The sleeve 20 is used in controls when the materials selected for the housing and the translatable element are not compatible. It may be seen that there need notbea sleeve 20 surrounding valve element 16. The housing around the translatable element could be provided with windows in such a fashion that translation of the movable element would realign the windows to meter fuel flow.

Problems of random flow fluctuation are encountered if proper consideration is not given to the design of the throttle valve and the sensing ports for constant pressure differential regulation. In state of the art designs, the velocity of the fuel entering the throttle valve is about ten feet per second. This velocity 'is dictated by the fact that high velocities cause unacceptable flow swirl and turbulence. These problems were magnified in the metering window area by flow perturbations due in part to variations in the discharge coefficient of the metering windows and problems associated with sensing reliable pressures. Fluctuation amplitudes of several percent have been caused by these flow defects. As a necessary consequence, the actual fuel velocity within the ducting has been limited.

In order to curb flow fluctuation and to obtain improved flow discharge coefficients in the metering .window area, a flow guide was designed for insertion into the throttle valve. The flow guide 32 has a curved base portion 34 to guide the flow out through the metering windows. Further, longitudinally of the movable element 16, the flow guide 32 had an extending partition 36 designed to reduce the swirl of the incoming fuel flow. This guide initially was attached to the translating element 16, and the partition portion 36 was aligned at a right angle tothe window opening. This particular design did not eliminate the effects of flow distortion. It was surprisingly learned, however, that a flow guide as originally designed could be inserted loosely into the translating element and would relocate itself to seek a position with minimum resistance to the flow. This reduced the fluctuation and perturbations resulting from the incoming flow variations and turning associated with metering flow. In practical application, the flow guide would probably be fixed.

FIG. 2 schematically illustrates the preferred location of the partition-portion 36 relative to the window openings l8'and 22. The guide angle .A should not be 90 and should fall generally within the 25 to 55 range. Angles less than 25 generally interfere with the window opening; and angles greater -than 55" generally cause unacceptable variations in flow. Thus, the application of a properly located simple device effectively curbs flow fluctuations inherent in miniaturized housing fuel controls. Flow. velocities as high as 40 feet per secondcan be employed with this guide.

Development has illustrated that tolerances can be assigned to various critical dimensions associated with the use of the flow guide. For example, the length of the flow guide should be about 2 times the internal diameter of the inner element. .Iudicious' location of the pressure taps improved the pressure regulation of the system. The selection of total pressure within the throttle valve after the flow has been straightened provides a very satisfactory pressure reading. Aswill be appreciated in referring to FIG. 1, upstream total pressure is admitted into chamber2l via the total pressure tap 23 disposed on either side of partition portion 36" and fed to the pressure regulator controller identified by the blank box 25. Likewise, static pressure downstream of the metering orifice is sent to the pressure regulator controller 25 via the static tap 27. The pressure regulator controller maintains a desired constant AP across the metering window by adjusting the pressure regulating valve 29 to control bypass flow. For details of a suitable pressure regulator reference is hereby made to U.S. Pat/No. 2.822.666, supra. and particularly FIG. 2 thereof.

It is, of course, apparent that the inner valve element in this particular throttlevalve translates and that the particular flow guide could bereadily adapted to valve elements which translate and rotate as long as the window position relative to the partition portion of the flow guide is maintained within about a 25? to 55 angle. While the partition has been shown as having planar surfaces, it is, of course, obvious to alter the surfaces thereby reducing the enclosed angle below 90 as intended by the instant invention. Many alterations to the partition can be simply incorporated, e.g., concave surfaces, partly curved and partly planar surfaces.

Although the preferred embodiment of this invention has been shown and described herein, it is to be understood that various changes and modifications may be made herein without departing from the spirit and scope of this invention.

I claim: A,

1. In a control, an improved throttle valve for metering at high flow velocity comprising:

a valve housing;

an inlet supplying fuel to the housing;

an inner valve element within the housing receiving the fuel supply and having a window and a close fitting sleeve with an aperture, means for translating one with respect to the other so that the window and aperture cooperate to meter the fuel supply according to a predetermined schedule;

a flow guide disposed within the inner valve element, and attached thereto, the flow guide having a base portion adjacent said window opening and adapted to turning the flow through said window and a partition portion extending longitudinally of the inner valve element and adapted to straightening the flow, the partition being located and aligned so that the enclosed angle between the partition and the window opening is less than 90; and

a collector receiving the metered fuel. I

2. A control as in claim 1, wherein the enclosed angle between the partition and the effective window opening is between 25 and 55.

3. A control as in claim 2 wherein the length of the flow guide is at least 2 times the internal diameter of the inner valve element.

4. A control as in claim 3, including means including a total pressure tap in the valve housing adjacent said partition portion for maintaining a constant pressure differential across the throttle valve by varying the fuel flow bypassing the throttle valve responsive to the total pressure upstream of the metering windows and the static pressure downstream of the metering windows.

5. In a throttle valve having inner and outer relatively movable valve elements for metering fuel at high flow velocities by the alignment of a window in the inner valve element with an aperture in the outer valve element, the improved method of curbing flow fluctuation, which comprises:

fixing a flow guide within the inner valve element, the flow guide having a base portion adjacent the window opening adapted to turning the flow through the metering windows and a partition portion adapted to straightening the incoming flow; and

locating and aligning the flow guide so that the enclosed angle between the partition and the window opening is less than 90.

6. The method ofclaim 5, including:

locating the flow guide so that the enclosed angle is between 25 and 55.

7. The method of claim 6, including:

selecting the guide so that the length of the guide is at least 2 times the internal diameter of the inner valve element. 

2. A control as in claim 1, wherein the enclosed angle between the partition and the effective window opening is between 25* and 55*.
 3. A control as in claim 2 wherein the length of the flow guide is at least 2 times the internal diameter of the inner valve element.
 4. A control as in claim 3, including means including a total pressure tap in the valve housing adjacent said partition portion for maintaining a constant pressure differential across the throttle valve by varying the fuel flow bypassing the throttle valve responsive to the total pressure upstream of the metering windows and the static pressure downstream of the metering windows.
 5. In a throttle valve having inner and outer relatively movable valve elements for metering fuel at high flow velocities by the alignment of a window in the inner valve element with an aperture in the outer valve element, the improved method of curbing flow fluctuation, which comprises: fixing a flow guide within the inner valve element, the flow guide having a base portion adjacent the window opening adapted to turning the flow through the meterinG windows and a partition portion adapted to straightening the incoming flow; and locating and aligning the flow guide so that the enclosed angle between the partition and the window opening is less than 90*.
 6. The method of claim 5, including: locating the flow guide so that the enclosed angle is between 25* and 55*.
 7. The method of claim 6, including: selecting the guide so that the length of the guide is at least 2 times the internal diameter of the inner valve element. 